JP2756636B2 - Gas analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas analyzer, and more particularly, to a gas analyzer for analyzing a gas discharged from an object to be measured into a vacuum system and a release speed of a component gas thereof.

[0002]

2. Description of the Related Art When a high vacuum is obtained, the gas released from the vacuum chamber itself becomes a problem.
In an ultra-vacuum or ultra-high vacuum system, analysis of gas released from a vacuum chamber is essential. Therefore, the material constituting the vacuum chamber is also required to be a material which emits a small amount of gas, and it is desired to accumulate and compare data on the gas emitted from various materials.

At present, the orifice method is widely used for the analysis of gas release rate and its components. FIG. 4 shows a basic configuration of a gas analyzer based on the orifice method as a conventional example. In FIG. 4, a measured chamber 6 as a sample is connected to a vacuum vessel 1 of a gas analyzer 10, and an orifice 2 is provided in the vacuum vessel 1.
Then, the conductance C _{10 of the} pipe including the orifice 2
Is known. The vacuum vessel 1 is provided with a total pressure gauge 3 and a partial pressure gauge 5 upstream of the orifice 2 and a total pressure gauge 4 downstream of the orifice 2.
Is connected.

The analysis by the gas analyzer 10 is performed as follows. Gas released from the measured chamber 6 as a sample connected to the vacuum vessel 1 is exhausted by the vacuum pump 7 via the orifice 2. By knowing the pressure P ₁ indicated by the total pressure gauge 3 and the pressure P ₂ indicated by the total pressure gauge 4 at this time, the gas release rate Q is calculated from the following equation (1). Q = (P ₁ -P ₂ ) C ₁₀ (1)

If necessary, the gas release rate Q is divided by the total surface area A of the sample, as shown in the equation (2).
The gas release rate q per unit surface area of the sample is determined. q = Q / A (2) Further, the components of the released gas can be known by the partial pressure gauge 5.

[0006] In the gas analyzer 10 of the orifice method, the gas release rate Q _m of the measuring instrument, such as whole pressure gauge 3,4 or potentiometer 5 is sufficiently small as compared with the gas release rate Q _s of the sample Has been ignored as. However, the fact is a These measurement instruments structure is complicated large surface area capable of adsorbing the gas, the gas release rate Q _m from these known large as comparable to the outgassing rate Q _s of the sample It became so. In other words, in the gas discharge rate Q obtained above, Q by addition to measuring instruments Q _s by the sample
_m will be included.

Although two total pressure gauges 3 and 4 are used, each measurement pressure has a measurement error, and
Further, obtaining the pressure difference between the two causes a large error range.

A gas analyzer 1 using the above-mentioned orifice method
Besides 0, also known gas analyzer according conductance modulation method includes the outgassing rate Q _m of the measuring device to the gas release rate Q obtained by this device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and does not include the gas release rate from a measuring instrument, and can analyze the gas releasing rate only from a sample. It is an object of the present invention to provide a gas analyzer having a small measurement error and, if necessary, a gas analyzer capable of analyzing the release rate of each component gas.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas analyzer for analyzing the release rate of a gas released from an object to be measured in a vacuum system, wherein a vacuum vessel is provided with an orifice provided therein. A pressure gauge is provided in an upstream space and a downstream space, and a pressure gauge is provided in the upstream space. At the time of analysis, the upstream of the vacuum vessel which is being exhausted from the flow path of the released gas is analyzed. A gas analyzer characterized in that a change in pressure caused by switching between a side space and the downstream space is measured by the pressure gauge.

[0011]

Since the gas analyzer of the present invention measures the pressure by switching the flow path of the gas to be released, the obtained gas release speed does not include the gas release speed from the measuring instrument. Furthermore, since only one pressure gauge is used for measuring the total pressure or the partial pressure, the error caused by the pressure gauge is small. Therefore, highly accurate analysis is possible as a whole.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic configuration of a gas analyzer according to the present invention will be described.

FIG. 1 is a diagram showing the basic configuration of a gas analyzer of the present invention for comparison with the basic configuration of a conventional gas analyzer 10 in FIG. Are given the same reference numerals. This gas analyzer 20 differs from the conventional gas analyzer 10 in that:
A gas flow path from the measured chamber 6 as a sample to the vacuum vessel 1 is branched, and one is connected to the upstream side of the orifice 2 as a main flow path and the other is connected to the downstream side of the orifice 2 as a sub flow path. The switching of these flow paths is performed by opening and closing the main flow path valve 8 and the sub flow path valve 9. Also, the total pressure gauge 4 downstream of the orifice 2 in the conventional example of FIG. 4 is omitted.

The discharged gas passing through the main flow path and the discharged gas switched through the sub flow path take the same route from a certain point between the orifice 2 and the vacuum pump 7 and thereafter. conductance C ₂₀ of the pipe containing the orifice 2 to full pressure gauge 3 is known in advance by measurement or calculation.

The gas analysis by the gas analyzer 20 is performed as follows. First, the main flow path valve 8 is opened,
The sub flow path valve 9 is closed, and the pressure P _1m at the time of the main flow path is measured by the total pressure gauge 3 while the gas discharged from the chamber 6 to be measured as a sample is exhausted by the vacuum pump 7. Next, the main flow path valve 8 is closed and the sub flow path valve 9 is opened, and the pressure P _1s in the sub flow path is measured by the total pressure gauge 3. Outgassing rate Q _s at this time is determined by the following equation (3). Q _s = (P _1m -P _1s ) C ₂₀ (3)

[0016] Hereinafter, will be explained that this equation (3) is not included Ne據that may be applied, and the gas release rate Q _m from the total pressure gauge 3 and potentiometer 5 in the equation (3). That is, although the pressure is not actually measured, the pressure at the junction where the flow path of the release gas passing through the main flow path and the flow path of the release gas passing through the sub flow path coincide with each other is P _2m for the main flow path. , P _{2s in} the case of the sub-flow path, the gas release speed Q _s from the sample, the gas release speed Q _m from the measurement device, and the gas release speed Q _p from the sample and the devices other than the measurement device added to the junction. Let S be the effective pumping speed at the point.

When the exhaust is performed in the main flow path, the exhaust balance at the junction is expressed by the following equation (4). _{Q s + Q m + Q p} = P 2m S ··········· (4)

When considering the gas passing through the total pressure gauge 3 and the partial pressure gauge 5, equation (5) is established according to equation (1). _{Q s + Q m = (P} 1m -P 2m) C 20 ····· (5)

On the other hand, when the flow is switched to the sub flow path, the exhaust balance at the junction is expressed by equation (6). _{Q s + Q m + Q p} = P 2s S ··········· (6)

In the case of the sub flow path, the gas released from the sample does not flow through the total pressure gauge 3 and the partial pressure gauge 5, so that the following equation is used.
(7) holds. Q _m = (P _1s -P _2s ) C ₂₀ (7)

Equation (8) is derived from equations (4) and (6). P _2m = P _2s (8)

Equation (9) is derived by subtracting equation (7) from equation (5). _{Q s = {(P 1m -P} 1s) - (P 2m -P 2s)} C 20 ··· (9)

Then, the above equation (3) is obtained by substituting the equation (8) into the equation (9). That is, according to the gas analyzer 20, only the gas release rate Q _s of the sample is determined,
All pressure gauge 3, except that there is no outgassing rate Q _m of the measuring device such as a potentiometer 5 including a gas release rate Q from than those
_{The presence of p} is not affected by it.

Further, since the pressure difference (P _1m -P _1s ) in the equation (3) is obtained by the same total pressure gauge 3, each measurement error and the difference as in the case of using two pressure gauges are obtained. The gas analyzer 20 of the present invention also has the advantage that the error due to the pressure gauge is small due to the fact that the error range is not expanded due to the determination.

When analyzing each component of the gas, the partial pressure gauge 5 is used according to the same principle, which will be described later.

Hereinafter, the configuration of the gas analyzer 30 of the embodiment will be described with reference to FIG.

A chamber to be measured 6 as a sample to be analyzed for the release rate of the released gas and its component gases is connected to the vacuum vessel 1 of the gas analyzer 30. The chamber to be measured 6 is a chamber made of stainless steel (SUS304L) and having an inner surface area of 0.46 m ^2. The inner surface is subjected to a GBB (glass bead blast) treatment and then heated at 450 ° C. in vacuum. An orifice 12 is provided in the vacuum vessel 1.
Conductance as may be selected is provided, which on to either the value of the conductance C of 0.01 m ³ s ^-1 or 0.001 m ³ s ^-1 in accordance with the magnitude of the gas release rate of the samples A variable mechanism 13 is added.

As the vacuum pump of the vacuum exhaust system, turbo molecular pumps 17 and 18 of the main exhaust system and a rotary pump 19
Are connected to the vacuum vessel 1, and a turbo molecular pump 21 and a rotary pump 22 as vacuum pumps of a sub-evacuation system are connected to the chamber 6 to be measured via the vacuum valve 16.

The gas flow path from the chamber 6 to be measured to the vacuum vessel 1 is provided with a three-way valve 11 via a vacuum valve 15, and a main flow path upstream of the orifice 12 and a sub flow path downstream thereof. And the switching of the flow path is made possible.

Further, as a pressure gauge, a total pressure gauge 3 and a partial pressure gauge 5 are mounted on the vacuum vessel 1 upstream of the orifice 12 and a total pressure gauge 4 is mounted downstream of the orifice 12. The total pressure gauge 4 is not used for gas analysis, but is used only when the conductance C is measured. Further, a reference pressure gauge 10 serving as a pressure standard is mounted on the upstream side of the orifice 12, and a total pressure gauge 14 is mounted on the sub exhaust system. Note that a hot cathode ionization vacuum gauge is used as a total pressure gauge, a mass filter type mass spectrometer is used as a partial pressure gauge, and a spinning rotor vacuum gauge is used as a reference pressure gauge.

Further, in order to heat and bake the region 30a including the vacuum vessel 1 and the region 23 including the chamber to be measured 6, a heating mechanism (not shown) is provided in each region.

The gas analyzer 30 according to the present embodiment is configured as described above. Next, the operation of the gas analyzer 30 and the analysis method based thereon will be described.

The vacuum vessel 1 has a vacuum pump 17 of a main exhaust system,
Evacuation is always performed by 18 and 19, and the vacuum valves 15 and 16 are in a closed state. The vacuum valve 16 is opened, and the evacuation of the chamber 6 to be measured is started by the vacuum pumps 21 and 22 of the sub-evacuation system.
^After confirming that the pressure reached ⁻⁴ Pa, the heating region 30 a of the vacuum chamber 1 and the heating region 23 of the measured chamber 6 were heated at 150 ° C. for 10 hours by the respective heating mechanisms. Next, the vacuum valve 16 was closed, the vacuum valve 15 was opened, and the three-way valve 11 was opened on the upstream side of the orifice 12 of the vacuum vessel 1, and the exhaust was switched to the vacuum pumps 17, 18, and 19 of the main exhaust system. Furthermore, after heating at 150 ° C. for 10 hours in this state, the whole was returned to room temperature and measurement was started. The conductance C is 0.01 m ³ s ⁻¹ at the time of heating.
0.001 m ³ s during measurement after room temperature
^{It was set to -1} .

In the measurement, the gas released from the chamber 6 to be measured is switched between the main flow path and the sub flow path at intervals of 30 minutes by the three-way valve 11, and the total pressure gauge 3 and the partial pressure gauge are switched 25 minutes after the switching to each flow path. The pressure was measured according to 5.

These operations, that is, starting the evacuation of the chamber 6 to be measured by the vacuum pumps 21 and 22 of the sub-exhaust system, heating and cooling the heating areas 30a and 23, and switching to the vacuum pumps 17, 18 and 19 of the main exhaust system. The operation and control of the gas analyzer 30 leading to the switching of the gas flow path at predetermined time intervals by the three-way valve 11 or the reading of the pressure values indicated by the total pressure gauge 3 and the partial pressure gauge 5 were automatically performed by a computer (not shown). .

FIG. 3 shows the measurement results obtained by the total pressure gauge 3 obtained as described above. The horizontal axis is time, the vertical axis is pressure,
This is the pressure indicated by the total pressure gauge 3 when flowing in the main flow path for the first 30 minutes and flowing in the sub flow path for the next 30 minutes. Arrow P _m ,
Shows the pressure P _{1 m} and P _1s at the time the arrow P _s is elapsed after start of the flow into the flow paths 25 minutes. P _m
= 1.5 × 10 ⁻⁷ Pa, P _s = 0.66 × 10 ⁻⁷ Pa, and the conductance C including the orifice 12 is 0.0
Since it is 01 m ³ s ⁻¹ , the gas release rate Q _s from the sample is obtained by the above equation (3) as follows. Q _s = 8.4 × 10 ⁻¹¹ Pam ³ s ⁻¹

The gas release rate for each gas component can be obtained from the ion current value observed by the partial pressure gauge 5 at the time of the main flow path and the time of the sub flow path. That is, the gas species of mass number N, because its partial pressure P _N and the ion current is observed at a partial pressure gauge 5 I _N is proportional, the proportionality factor K
Assuming that _N is the ion current value in the main flow path, I _Nm is the ion current value in the sub flow path, I _Ns is the ion current value in the sub flow path, and C _N is the conductance of the gas type, the gas release rate Q _N is given by the following equation (3).
Equation (10) as a modification of Similar to _{Q N = K N (I Nm} -I Ns) C N ········ (10) as described above, the gas release rate Q _s of the gas release rate Q _N also total gas of each gas component Can be sought.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these, and various modifications can be made based on the technical concept of the present invention.

For example, in the embodiment, the total pressure gauge 3 and the partial pressure gauge 5 are provided on the upstream side of the orifice 12 of the vacuum vessel 1, but depending on the purpose, only the total pressure gauge 3 or the partial pressure gauge 5 may be provided.

In the embodiment, a hot cathode ionization vacuum gauge is used as the total pressure gauge 3. However, any type of vacuum gauge can be used as long as it can measure a high vacuum equivalent to this. Furthermore, although a mass filter type mass spectrometer was used as the partial pressure gauge 5,
Other mass spectrometers may be used.

In the embodiment, the variable conductance type orifice 12 is provided. However, the variable conductance type orifice may not be used, and a pipe having a known conductance may be provided instead of the orifice.

In the embodiment, the three-way valve 11 is used for switching between the main flow path and the sub flow path of the gas to be released. However, two vacuum valves for opening and closing each flow path can be used instead. .

In the embodiment, the gas analyzer 30
The analysis of the gas released from the measured chamber 6 connected to the above has been described, but the gas in the vacuum device can be analyzed by introducing a gas or connecting a vacuum device that generates the gas. is there. Further, it is also possible to analyze the gas release from the material specimen accommodated therein by using the measured chamber 6 in this embodiment as a sample chamber.

[0044]

According to the gas analyzer of the present invention, the obtained gas release rate does not include the gas release rate from the measuring instrument, and further, the error caused by the pressure gauge is small. , A highly accurate analysis result can be obtained.
In addition, the gas analyzer of the present invention has a low manufacturing cost because the number of expensive pressure gauges is small.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a gas analyzer according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a gas analyzer according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a gas flow path and a pressure measured by the apparatus of the embodiment.

FIG. 4 is a block diagram showing a basic configuration of a conventional gas analyzer.

[Explanation of symbols]

 Reference Signs List 1 vacuum vessel 2 orifice 3 total pressure gauge 4 total pressure gauge 5 partial pressure gauge 6 chamber to be measured 7 vacuum pump 11 three-way valve 12 orifice 17 vacuum pump 18 vacuum pump 19 vacuum pump 21 vacuum pump 22 vacuum pump

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sakae 5-9-7 Tokodai, Tsukuba, Ibaraki Pref. Tsukuba Super Materials Research Laboratories, Japan Vacuum Engineering Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 7/00-7/22 JICST file (JOIS)

Claims (3)

(57) [Claims] In a gas analyzer for analyzing a release rate of a gas released from an object to be measured into a vacuum system, a vacuum vessel is divided into an upstream space and a downstream space by an orifice provided therein. A pressure gauge is provided in the upstream space, and at the time of analysis, the flow path of the released gas is switched between the upstream space and the downstream space of the vacuum vessel being exhausted. A gas analyzer characterized by measuring a change in pressure caused by the pressure with the pressure gauge. 2. The gas analyzer according to claim 1, wherein the pressure gauge is one or both of a total pressure gauge and a partial pressure gauge. 3. The gas analyzer according to claim 2, wherein the total pressure gauge is a hot cathode ionization vacuum gauge, and the partial pressure gauge is a mass filter mass spectrometer.